Studies On Biological And Ecological Characteristics Of Dysmicoccus Neobrevipes Beardsley

Dysmicoccus neobrevipes Beardsley is a new invasive exotic pest which has been recently found in China.. So in this paper, we carried out a systematic study on the morphological characteristic, living habits, reproduction mode, developmental durations, developmental threshold temperature, effective accumulated tempeature of this pest. Meantime, the life table of the laboratory population fed on pumpkin was constructed at different temperatures(20, 23,26, 29, 32?) to provide a valid experimental evidence and theoretical basis for this pest. The main research results were as follows:The morphological characteristics of D. neobrevipes at developmental stages were observed and described in detail. The habits of D. neobrevipes, which including hatching, feeding, molting, pupating,emergence, oviposition and so on were also observed. D. neobrevipes was consisted of three stages which is egg, nymph and adult in the life cycle of female, The nymph was comprised of three instars.while in male, it was consisted of four stages which is egg, nymph, pupa and adult. The studies on the reproduction mode of D. neobrevipes had shown that all reproduction mode of the mealybug was sexual reproduction,and both male and female could be multi-mating. Under the tested conditions,the mated female adult could normally lay eggs, while the unmated female adult could not, but with longer survival time.Temperature had a significant effect on the development of D. neobrevipes at constant temperature 20-29 ? range, the developmental durations of every stage of D. neobrevipes were all decreased with the increasing temperatures, under 20? both female and male nymph D. neobrevipes has the longest duration 46.95d and 50.26d respectively; It is interesting that female and male nymph D. neobrevipes grow most fast under 29? (20.28d) and 32? (20.70d). The temperature had significant effects on survival rate of D. neobrevipes. With temperature range of 20-29?, the survival rate increased with temperature. The relationship between the developmental rate and temperature for each stage could be simulated by the quadratic regression. The developmental threshold temperature of female and male was 13.80? and 11.61 ?, and effective accumulated temperature of females and male was 491.50 and 388.85 day-degrees respectively. The temperature effected female reproduction significantly. Both pre-oviposition duration and adult longevity decreased with increasing the temperature, and highest fecundity per female was 442.21 at 29?, while the lowest was 111.83 at 20?. The population trend index (I) were larger than 1 at 20-29?. the population trend indexes under 20? and 29? were 19.12 and 168.18 respectively. At 17? and 32 ?, D. neobrevipes of the 1st instar nymphs and 3rd instar nymphs were found to stop growth. It showed that the population development ability of D. neobrevipes was strong, but excessively high or low temperatures were not suitable for the population growth of the D. neobrevipes.